1. Technical Field of the Invention
The present invention relates to a troubleshooting method and a communication system by which a communication trouble such as mistranslation of data can be detected and a trouble factor can be specified, in a loop-structure network.
2. Prior Art
There is a conventionally known troubleshooting system for a communication apparatus in a loop structure network, as disclosed in Open-laid Japanese Patent Application KOKAI Publication No. 63-246946.
In the troubleshooting system, a monitor communication apparatus sets a monitor indicator in a data frame, and another communication apparatus which receives the data frame resets the monitor indicator when transmitting the data frame. Therefore, in case where the monitor communication apparatus receives a monitor indicator already set, it means that an abnormal data frame which has not been received by any communication apparatus has occurred.
Accordingly, when such an abnormal data frame is detected, the monitor communication apparatus detects the address of the sender or receiver of the abnormal data frame. As a result of this, the communication apparatus which causes the trouble can be specified.
However, in such a troubleshooting system for a communication apparatus in a conventional loop structure network, for example, when a monitor indicator which should have been set and transmitted is reset and transmitted by a trouble in a monitor communication apparatus, even a data frame transmitted from a communication apparatus causing a trouble has a reset monitor display, and therefore, there is a problem that detection of a communication apparatus causing a trouble is impossible.
In addition, in a monitor communication apparatus, the communication apparatus causing a trouble is detected by receiving a data frame having a monitor indicator set as above. As a result of this, there is a problem that it is impossible to detect the communication apparatus causing a trouble in case where a monitor indicator is reluctantly reset and transmitted, even though a trouble is caused in the communication apparatus.
Also, in a monitor communication apparatus, the communication apparatus causing a trouble is detected by receiving a data frame having a set monitor indicator. Therefore, there is a problem that a communication apparatus is erroneously detected as causing a trouble if a monitor indicator reluctantly is set and transmitted even though the communication apparatus does not cause a trouble.
Further, the communication apparatus causing a trouble is specified by detecting the address of a sender or receiver of an abnormal data frame. Therefore, there is a problem that the communication apparatus causing a trouble cannot be correctly detected if the source address or receiver address itself is incorrect.